Such was the savagery of the beating doled out by Neil Lennon's side on Sunday it was a surprise the game reached the 90th-minute mark without the RSPCC stepping in to appeal for clemency.
Hearts' group of young players have endured plenty this season as they thrash around at the foot of the table but Celtic were not of a mind to go easy on them, rattling in seven goals and threatening to score several more. It was the perfect riposte to the suggestion they would have little appetite for their domestic fayre after tumbling out of Europe earlier in the week.
Danny McGrain watched it all unfold from the away dug-out at Tynecastle with a smile on his face. Did he feel any sympathy for Hearts? The Celtic first-team coach looked so puzzled by the question it was as if it had been asked in Mandarin. Clearly, there is a time and a place to show mercy and a fourth round William Hill Scottish Cup tie is not it.
"It was magnificent," he said. "It was a great reaction. Even before the game there wasn't a feeling in the dressing room of not looking forward to it. Once the manager spoke to the players at the hotel and got them going, he wanted them to win. To win by two or three, and do it confidently, would've been nice enough. But to win the way we did, it just blew everybody away.
"You don't feel sorry for anyone. You don't even think about your opponents. You can't have sympathy for anybody. They were pummelled - given a lesson. But we were looking for eight even when we got seven. That used to be the old schoolboy thing, didn't it? If you scored 10 at half-time the coach would say to stop at 15. Okay they are a young Hearts team but they've beaten Aberdeen twice this season. No one called them a young team then. If they are a young team they'll have learned something from the game. What that is, I don't know."
McGrain spent the best part of two decades as a Celtic player and helped hand out a few heavy beatings of his own. The former full-back recalled Celtic's 5-0 win at Love Street on the final day of the 1985/86 season - when the title was whisked away from Hearts' grasp on goal difference - as a match that bore comparison to Sunday's trouncing.
"A game I do remember when we played as well as was at St Mirren when we won 5-0," he recalled. "We had no fear, Hearts were going to win the league, we went out and played with a freedom. We played amazing football that day. I would relate how we played at Tynecastle to that day. The performances were similar. Everybody played well against St Mirren, everybody played well [on Sunday]. When you play the way we did, it's going to be hard to replicate that. After we beat St Mirren 5-0, I didn't think we'd ever play that way again.
"These [Celtic] players will get huge confidence from what they did. Their next game is against Motherwell, who lost to Albion Rovers at the weekend, so they'll be getting the sleeves rolled up knowing we've just scored seven goals against Hearts. They won't want a doing. Teams will have seen our performance and will realise they'll have to play with added impetus against us. No one else will want to be beaten 7-0 by us."
Mikael Lustig embroidered another impressive performance at right-back with the best goal of the lot, advancing from defence to unleash a venomous shot that crashed over Jamie MacDonald and kissed the crossbar on its way in. McGrain believes in Lustig, the injured Adam Matthews and Darnell Fisher, Celtic are spoiled for choice in his old position.
"Mikael was just magnificent. We've got him, Adam Matthews and young Darnell Fisher vying for one place once Adam's back. The manager does well with them to play two or three games at a time. Mikael's goal was just magnificent. I don't know how he had the time to do it but it was just a great strike of the ball. People don't remember but I scored some like that - two at Barrowfield and one at Airdrie."
Sunday's game at Tynecastle was Lennon's 200th as manager and McGrain sees a manager who is maturing with every match. "He's been brilliant," he said. "He's grown as a manager mentally and he's still learning. I'm sure he's learnt a great deal from European ties against such big names. He knows his players better than anybody. And Garry [Parker] and Johan [Mjallby] work hand-in-hand with him. They all work together."